You've got a minimum of 3 different concepts in there
1. Success - and getting what you are going after is a reasonable definition
2. Happiness - you seem to be suggesting this is the real purpose of getting success. I disagree. Happiness can come without success as defined above. In fact waiting for happiness this way is a formula for mid-life crisis.
Here's an eloquent video of the science - get at least 3 minutes in to get hooked...
TED | Talks | Dan Gilbert: Why are we happy? Why aren't we happy? (video)
3. Purpose - ah, well. Different again. You may go after a purpose and NEVER achieve it ie succeed, but it was still worth doing.
If it helps...